Correct Chainlength For 1x9 Setup?

How do you work out how long your chain should be on a 1x9 set up? I've always used big ring/small sprocket and jockey wheels vertically inline for 3x9 set up, does this still apply?

A quick search on here found Park Tools answer:

SIMPLE EQUATION: L = 2 (C) + (F/4 + R/4 + 1)

L = Chain length in inches. Round the final result to closest whole inch figure.
C = Chain stay length in inches, measure to closest 1/8”. Use chart below to find decimal measurement.
F= Number of teeth on largest front chainring.
R= Number of teeth on largest rear cog.

Shift the bike into 1st.
Remove shock spring/air from shock.
Compress the suspension.
Fit the chain, add or remove links until the mech is almost at full stretch.

If its 1x9 on a hardtail then

Shift the bike into 1st.
Fit the chain, add or remove links until the mech is almost at full stretch.

job done.

been using this method for 10 years

you will find if you "guess" the chian length the chain maybe too short this will have a massive effect on suspension action. the chain may stop the bike getting full travel. leading to snapped chains or at worse ripped off mech hangers from frames. too slack and the chain will flap around all over the place

Wrap the chain round your chain ring cog (without going through rear mech. Then around the largest cog on the cassette, note where they meet add +3 for shimano chains without quick link and +2 + quick link for KMC/SRAM chains.

more or less chain passing through the mech depending on the mech length. adding two links maybe too much for a short cage mech - leading to incorrect chain length
and maybe too short for a long cage mech leading to incorrect chain length

@ Greeble, thanks for the explanation. But i thought adding in the 2 extra links accomodates the rear mech? I actually add 3 as this is what it said to do in a book I had. 3 for shimano and 2+ quick link for chains with quick link.

+ 2 links we know works for a long cage mech on a 3 x 9 or whatever setup, with a 1 x 9 setup the overall tooth capacity is smaller so a mtb short cage mech can be used & because of the length of the mech a shorter chain might be able to be used - I would go with +2 links, try it & if too long take another link out (easier to remove 1 than add 1 afterall)

Mboy - sorry I don't see it - when in big / big the chain is almost straight along its bottom run - the short road mech and the long mtb mech I have are both the same and taking another link out would make the chain too short on the road mech despite it being much shorter mech - its still big / big + two links is the shortest chain possible

Edit - the plus 2 links is not a good start for 1 x 9, the formula for 3 x 9 is big to big plus 2 links is only okay because you should never actually ride big to big. Setting up a 1 x 9 in the same manner will prob result in too short a chain when riding on the largest sprocket.

Edit - the plus 2 links is not a good start for 1 x 9, the formula for 3 x 9 is big to big plus 2 links is only okay because you should never actually ride big to big. Setting up a 1 x 9 in the same manner will prob result in too short a chain when riding on the largest sprocket.

Hense why this...

Best and most trusted 1x9 chain length calculator I've used is -

Shift the bike into 1st.
Remove shock spring/air from shock.
Compress the suspension.
Fit the chain, add or remove links until the mech is almost at full stretch.

If its 1x9 on a hardtail then

Shift the bike into 1st.
Fit the chain, add or remove links until the mech is almost at full stretch.

I agree with the general consensus but be careful when setting up a full suspension bike as the longest effective chain length on many bikes, including mine as I found out to my cost, is not at either end of the travel but about 1/3rd of the way through. My bike has a VPP link system so the path of the rear wheel is backwards and then up in a sort of C shape. As a result there needs to be enough slack in the chain to allow for the suspension to follow its path.

Oooh, if you want a tatty, but functional, short cage version of the same, I still have one kicking about somewhere I think from when I ditched 9spd to go to 10spd. Short cage definitely helps reduce chain slap and aids keeping the chain on in a single ring setup.

Just checked mine & with the rear mech as taught as I'd be prepared to go (ie still making a S shape in the chain) mine is just about big to big plus 3.25 links with a short MTB mech - on a hardtail frame.